Physical Properties of Hydrogen
Hydrogen is the only element in the periodic table in which valence orbital electron under the direct influence of the nucleus or there is no shielding electron with symbol H and molecular formula H2. The atomic and mass number of hydrogen is one with electronic configuration 1s1. Due to the presence of one electron is 1s-orbital, hydrogen forms a wide range of chemical bonding like the normal covalent, ionic, bridge, or hydrogen bonding between other atoms. Hydrogen has three isotopes like protium deuterium and tritium form three covalent molecules like di-hydrogen, di-deuterium, and di-tritium uses as an alternate fuel or energy sources for our environment. On the earth’s surface, hydrogen gas molecule is the third most abundant element after oxygen and silicon and 2nd most abundant gases after oxygen.
Position in Periodic Table and Bonding
The ns1 electronic configuration hydrogen justifies the position in group-1 with alkali metals having very low ionization energy. Consider otherwise, the electron configuration is just one electron short of the next noble gas helium in chemistry. Therefore it may be placed in group-17 with the halogen having very high electronegativity and affinity. Due to the presence of the half-filled valence shell, hydrogen also placed group-14 with carbon forming a wide range of covalent bonding with a wide range of polarity. Normally the oxidation number of hydrogen = +1, but due to unique behavior hydrogen also shows -1 oxidation state in LiH, NaH, CsH, CaH2, etc.
Chemical Properties of Atomic Hydrogen
Hydrogen is the most abundant element that does not occur free in the earth’s atmosphere. Because the kinetic energy at the earth’s temperature is sufficient to escape from the earth’s gravitational energy to decreasing the density of the H-gas. The hydrogen molecule is the very stable species due to high bond energy even at 2000°K, there is only one percent atomic hydrogen present in the H2-gas molecule. The half-life of atomic hydrogen nearly 1 second at 0.2 mm pressure and huge heat uses for recombination about 432.6 kJ mol-1. Therefore, this process uses for high-temperature welding of metals tantalum and tungsten. Due to high reactivity, H-atom is a strong reducing agent that reduces ethylene, hydrogen peroxide, and metal ions.
Hydrogen atom absorbed energy to shift its electron particles to different energy levels. The electrons in higher energy levels are relatively unstable and hence drop back to the lower energy level to produce the electromagnetic spectrum.
Nuclear Spin Isomers
When the nucleus of an atom contains an odd number of nucleons, the nucleus has a resultant spin. If such two atoms combine to form the diatomic molecule the nuclei may have parallel or anti-parallel spins. This is called nuclear spin isomerism. The molecule in which the two nuclei have a parallel spin called ortho-isomer and the molecule with antiparallel nuclear spins called para-isomer. Such nuclear spin isomer found in H2, D2, T2, N2, O2, etc.
The conversion para-H2 to ortho-H2 and vice versa are normally very slow. They involved the forbidden transition between two energy states of the different spin municipality. The introduction of H-atom or the use of catalysts like oxygen, nitrous oxide, nitrogen dioxide, platinum, palladium, and charcoal accelerate the attainment of equilibrium. The used catalyst is paramagnetic.
Uses of Molecular and Atomic Hydrogen
- H2 uses for the production of ammonia for industrial purposes.
- It is used to manufacture hydrochloric acid, sulfuric acid, nitric acid, methyl alcohol, etc. Methyl alcohol prepared by oxo process subsequently oxidized to formaldehyde which uses for the synthesis of plastics.
- In hydroformylation reaction or the addition of H2 and formyl group into unsaturated hydrocarbon like alkenes. The produced aldehydes subsequently changed to alcohol. These are uses for the preparation of PVC resin and detergents.
- H-atom used for welding high melting metals like tantalum and tungsten.
- Reduction of metal oxides. Direct reduction of iron ore developed on a commercial basis for the preparation of iron metal.
- Liquid H2-molecules uses in the population of rockets and bubble chambers.
- H2 uses in the hydrogen-oxygen fuel cells for energy generation to mankind.
- Hydrogen spectrum uses for organic molecular structure determination.
Uses of Protium Deuterium and Tritium
Deuterium oxide or D2O is largely used as heavy water in nuclear power plants. D2O also used as a source of deuterium compounds. Thus deuterium uses to study the physical and chemical properties kinetics reaction mechanism and reaction order determination. Titanium widely used as a tracer element due to its radioactivity.